객관식
A particular sample of vinegar has a pH of 2.90. If acetic acid is the only acid that vinegar contains, what is the concentration of acetic acid in the vinegar?
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17. Acid and Base Equilibrium
pH of Weak Acids
객관식
Calculate the pH of the solution made by adding 0.50 mol of HOBr and 0.30 mol of KOBr to 1.00 L of water. The value of Ka for HOBr is 2.0 × 10⁻⁹. What is the pH of the solution?
A
9.26
B
4.74
C
3.00
D
7.00
검증된 단계별 안내1
Identify the components of the solution: HOBr is a weak acid and KOBr is its conjugate base. This is a buffer solution.
Use the Henderson-Hasselbalch equation to find the pH of the buffer solution: \( \text{pH} = \text{pKa} + \log \left( \frac{[A^-]}{[HA]} \right) \).
Calculate \( \text{pKa} \) using the given \( \text{Ka} \) value: \( \text{pKa} = -\log(\text{Ka}) \). Substitute \( \text{Ka} = 2.0 \times 10^{-9} \) into the equation.
Determine the concentrations of the acid \([HA]\) and the conjugate base \([A^-]\): Since the solution is 1.00 L, \([HA] = 0.50 \text{ M}\) and \([A^-] = 0.30 \text{ M}\).
Substitute the values of \( \text{pKa} \), \([A^-]\), and \([HA]\) into the Henderson-Hasselbalch equation to calculate the pH.
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